Inspection method and apparatus, lithographic apparatus, lithographic processing cell and device manufacturing method

Abstract

A device manufacturing method is disclosed. A radiated spot is directed onto a target pattern formed on a substrate. The radiated spot is moved along the target pattern in a series of discrete steps, each discrete step corresponding to respective positions of the radiated spot on the target pattern. Measurement signals are generated that correspond to respective ones of the positions of the radiated spot on the target pattern. A single value is determined that is based on the measurement signals and that is representative of the property of the substrate.

What is claimed is: 
     
       1. A method of measuring a property of a substrate comprising:
 directing a radiated spot onto a target pattern formed on the substrate; 
 moving the radiated spot along the target pattern in a series of discrete steps, each discrete step corresponding to respective positions of the radiated spot on the target pattern; 
 generating measurement signals that correspond to respective ones of the positions of the radiated spot on the target pattern; and 
 determining, based on the measurement signals, a single value that is representative of the property of the substrate. 
 
     
     
       2. The method of  claim 1 , wherein the determining further comprises:
 correcting the measurement signals using respective reference signals that correspond to the respective positions of the radiated spot on the target pattern; and 
 deriving, based on the corrected measurement signals, the single value. 
 
     
     
       3. The method of  claim 2 , wherein the correcting further comprises correcting one or more of a DC level, ghost image correction, intensity level, or illumination shape. 
     
     
       4. The method of  claim 1 , wherein the determining further comprises:
 correcting the measurement signals using respective reference signals that correspond to the respective positions of the radiated spot on the target; 
 deriving values that are representative of the property of the target pattern at the respective positions on the target pattern, the values being derived based on respective ones of the corrected measurement signals; and 
 deriving, based on the values, the single value. 
 
     
     
       5. The method of  claim 4 , wherein the correcting further comprises correcting one or more of a DC level, ghost image correction, intensity level, or illumination shape. 
     
     
       6. The method of  claim 1 , wherein the determining further comprises:
 combining the measurement signals to output a combined signal; and 
 deriving, based on the combined signal, the single value. 
 
     
     
       7. The method of  claim 1 , wherein the determining further comprises:
 determining an average value of the measurement signals; and 
 deriving, based on the average value, the single value. 
 
     
     
       8. The method of  claim 1 , wherein the determining further comprises:
 determining a median value of the measurement signals; and 
 deriving, based on the median value, the single value. 
 
     
     
       9. The method of  claim 1 , wherein the radiated spot is smaller than the target pattern in a dimension along a length of the target pattern. 
     
     
       10. The method of  claim 1 , wherein the measurement signals correspond to lines of a grating structure formed on the surface of the substrate. 
     
     
       11. The method of  claim 10 , wherein the directing comprises directing the radiated spot over at least two lines of the grating structure. 
     
     
       12. The method of  claim 1 , wherein the moving comprises moving the radiated spot such that each of the respective positions of the radiated spot overlap with an adjacent one of the respective positions. 
     
     
       13. The method of  claim 1 , wherein the single value represents a critical dimension (CD), overlay calculation, or focus dose calculation. 
     
     
       14. The method of  claim 1 , further comprising:
 determining one or more variation parameters associated with the measurement signals, 
 wherein the one or more variation parameters include a variance, standard deviation, minimum value confidence level, maximum value confidence level, mode, or outlier identification. 
 
     
     
       15. The method of  claim 14 , further comprising:
 determining a spread of the single value over the target based on the variance of the measurement signals. 
 
     
     
       16. The method of  claim 14 , further comprising:
 removing one or more outliers associated with the measurement signals based on the outlier identification.